The present invention concerns shielding of electronic equipment, and more specifically a method of manufacturing shield cans utilized for such shielding. The shield can is used to protect electronic equipment from interfering radiation and is often a combination of a plastic housing, a conductive layer and a conductive gasket. The conductive layer is in electrical contact with a printed circuit board of the electronic equipment.
To protect electronic equipment against interfering radiation some kind of conductive shield is normally placed on or in connection with a printed circuit board of the electronic equipment. Such a shield functions also to reduce the risk that the electronic equipment itself disturbs other surrounding electronic equipment.
A shield of this kind often has the form of a shield can comprising a plastic housing, a conductive layer on the inside of the housing and a conductive gasket. The conductive layer should be in electrical contact with the printed circuit board.
According to the prior art a shield can is normally manufactured in three steps. First the housing of the shield can is moulded by injection moulding. The next step is to make at least one of the surfaces of the shield electrically conductive by some kind of surface treatment. Finally a gasket is added, which in the prior art often has been done by over-moulding on the plastic housing. After assembly the shield can shall be in electrical contact with the printed circuit board.
The above different steps of manufacturing the shield can, are almost never provided by the same manufacturer. This means that the shield can must be transported between the different manufactures to be handled in the different processes, causing high logistic costs. Handling of the shield can in several moulds in different processes and locations causes tolerance problems.
When the gasket is moulded over the plastic housing, the plastic will often be deformed. Furthermore, the shield can is handled in at least two moulds and every time the shield can is ejected from a mould there is a clear risk that the shield can will get small scratch marks. The above leads to a rather high rejection rate for shield cans manufactured according to the prior art, especially if the shield can is a cosmetic part, e.g. the back cover of a mobile telephone.
To overcome the above problems, according to the invention the shield can is manufactured in one single tool, i.e. one single mould, by means of a multi-k procedure.
Instead of surface treatment as in the prior art a conductive inlay, such as a foil, cloth or the like is used. The conductive inlay is pre-formed and then placed in the mould. By using a so-called 2-k (xe2x80x9czwei Komponentenxe2x80x9d) mould procedure a plastic housing is first formed on one side of the inlay. In a subsequent step a conductive gasket is formed on the other side of the inlay.
By using the conductive inlay in the mould and a 2-k mould procedure it is possible to mould complete shield cans having a conductive layer and a conductive gasket in one single mould. Instead of transporting a plastic shield can two or more times, lightweight non-space demanding inlay is transported once. Tolerance problems that occurs in the prior art of moulding gaskets over a plastic housing are eliminated due to that only one tool is used. The shield can is only handled in one process reducing the risk of scratches and other damages. The reduced risk of damages will lower the reject ratio, especially if the shield can is a cosmetic part.
It should be emphasised that the term xe2x80x9ccomprises/comprisingxe2x80x9d when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
As used in this description the term xe2x80x9cconductivexe2x80x9d is to be understood as electrically conductive, if not stated otherwise.